METALS 285 
surface, but quickly becomes covered with a grayish- 
yellow powder-dross. This is an Oxide of Lead, and very 
poisonous—as are all the compounds of this substance, 
such as red-lead and white-lead (also Lead Oxides) both of 
which are used by painters in the preparation of their 
colours. Notice that, although readily fusible, it does not 
burn. 
Make a clean cut through a leaden bullet, press the cut 
surfaces together with a slight twisting motion, and notice 
that they adhere with great tenacity. 
Uses. The uses of Lead depend chiefly on its mal- 
leability, fusibility, flexibility, and its want of elasticity. It 
is used in sheet-form for roofing houses, for making gutters 
on houses, for covering the floors of bathrooms, and for 
lining cisterns. It can easily be bent or cast into any form 
and is used for making water and gas pipes, shot and 
bullets. When rolled out into thin sheets, it forms the 
lining for tea-chests. 
Preparation. The metal is obtained either from the 
Sulphide or the Oxide Ore—the former, Galena, being the 
principal Ore of commercial importance. 
The Ore Galena is first sorted, then crushed to a powder 
in a stamping mill, and washed to remove the earthy 
matters. After this it is roasted to get rid of the Sulphur, 
and then smelted. The smelting causes the remaining 
Impurities to be removed, the volatile portions as gas, and 
the solid portions in the shape of slag. The heavier metal 
then sinks to the bottom of the furnace and is drawn off 
into iron pans. 
NoTE.—Lessons on the metals can be begun in the lower classes, 
where a simple treatment will pave the way for a more detailed 
investigation in the upper standards. All the commoner metals, 
Zine, Tin, Copper, can be treated in some such way as that de- 
tailed in this chapter. Lessons on the precious metals will also 
prove of interest ; but these are more suitable for schools within 
reach of gold-mining districts, where pupils are more or less con- 
versant with the work of the mining community. 
